Helppp please!! I do not understand.

1. [10.9 Points] DETAILS be; Submissions Used MY NOTES On what interval(s) is the function f(x) : x8 8x7 both decreasing and concave up? (Enter your answer using interval notation.) . Submit Answer 2. [40.9 Points] DETAILS 0/6 Submissions Used MY NOTES 1 On what interval(s) is the function f(x) = x 4 14x13 + 8 both increasing and concave up? (Enter your answer using interval notation.) Submit Answer 3. [-10.9 Points] DETAILS 0/6 Submissions Used MY NOTES On what interval(s) is the function f(x) = x5 5x4 + 1 both decreasing and concave down? (Enter your answer using interval notation.) : Submit Answer 4. [-10.9 Points] DETAILS 0/6 Submissions Used MY NOTES On what interval(s) is the function f(x) = x7 7x6 + 15 both increasing and concave up? (Enter your answer using interval notation.) 5. [-10.9 Points] DETAILS -_ 0/6 Submissions Used MY NOTES 7 On what interval(s) is the function g(x) = e'g" both decreasing and concave clown? (Enter your answer using interval notation.)